Pressure sensing implant

Abstract

A wireless circuit includes a housing having at least one opening, and sensor connected to the housing at the opening. The sensor includes a first layer having a first dimension and a second layer having a second dimension shorter than the first dimension. The second layer may be positioned entirely within the housing and a surface of said first layer may be exposed to an exterior of the housing.

Having thus described the invention, we claim: 
     
         1 . A circuit comprising:
 a housing comprising a plurality of walls defining a first cavity and an opening;   a sensor connected to the housing at the opening, the sensor comprising:
 a lid wafer comprising an electrode; and 
 a base wafer comprising an electrode, wherein the base wafer is positioned entirely within the first cavity and the base wafer is bonded to the lid wafer, the lid wafer and base wafer defining a second cavity, wherein the second cavity comprises a port to allow fluid communication with the first cavity. 
   
     
     
         2 . The circuit of  claim 1 , wherein the sensor is a capacitive pressure sensor. 
     
     
         3 . The circuit of  claim 1 , wherein the sensor is connected to the housing at the opening to hermetically seal the housing. 
     
     
         4 . The circuit of  claim 1 , wherein a second surface of the lid wafer is accessible from inside the housing. 
     
     
         5 . The circuit of  claim 1 , wherein the lid wafer, the base wafer, and the housing are comprised of any combination of glass, silicon, or another ceramic. 
     
     
         6 . The circuit of  claim 1 , wherein an antenna is located within the housing. 
     
     
         7 . The circuit of  claim 6 , wherein an antenna axis is substantially parallel to at least one wall of the housing. 
     
     
         8 . The circuit of  claim 1 , wherein the circuit is configured to be implanted in a blood vessel. 
     
     
         9 . The circuit of  claim 1 , wherein the housing is filled with a substance selected from a group including: liquid, gel, vacuum, inert gas, or air. 
     
     
         10 . The circuit of  claim 1 , wherein the housing comprises an internal component comprising at least one of a battery, stimulus electrode, pacing circuitry, flow sensor, and chemical sensor. 
     
     
         11 . The circuit of  claim 1 , wherein the electrode of the lid wafer comprises slots or breaks that result in a non-continuous solid area for preventing formation of eddy currents during operation of the sensor. 
     
     
         12 . The circuit of  claim 1 , wherein the lid wafer comprises a second electrode. 
     
     
         13 . A circuit comprising:
 a housing comprising a plurality of walls defining a cavity and an opening;   a sensor connected to the housing at the opening to form a hermetic seal, the sensor comprising:
 a lid wafer having a first surface and a second surface wherein the first surface is exposed to an exterior of the housing, and an electrode positioned on the second surface of the lid wafer; 
 a base wafer having a first surface bonded to the second surface of the lid wafer and having an electrode positioned on the first surface of the base wafer; and 
 wherein the base wafer is positioned entirely within the cavity and the electrode pm the lid wafer comprises slots or breaks that result in a non-continuous solid area for preventing formation of eddy currents during use of the sensor. 
   
     
     
         14 . The circuit of  claim 13  further comprising a second cavity between the lid wafer and the base wafer. 
     
     
         15 . The circuit of  claim 14 , wherein the second cavity between comprise a port to allow fluid communication with the first cavity. 
     
     
         16 . The circuit of  claim 13 , wherein the lid wafer comprises a second electrode. 
     
     
         17 . A circuit comprising:
 a housing defining a cavity and an opening;   a capacitive plate positioned on a lid wafer, wherein the lid wafer comprises a first surface, an opposite second surface and an electrode positioned on the second surface;   a second capacitive plate positioned on a base wafer, wherein the base wafer comprises a first surface and an opposite second surface, the second capacitive plate is positioned on the first surface and a portion of the first surface of the base wafer is bonded to the second surface of the lid wafer forming a sensor; and   an electronic assembly inserted within the cavity of the housing, wherein the sensor is bonded to the opening of the housing and the base wafer is positioned within the cavity defined by the housing.   
     
     
         18 . The circuit of  claim 17 , wherein the capacitive plate on the second surface of the lid wafer comprises slots or breaks that result in a non-continuous solid area for preventing the formation of eddy currents during use of the sensor. 
     
     
         19 . The circuit of  claim 17  further comprising side walls attached to the housing to form a hermetic seal in the housing. 
     
     
         20 . The circuit of  claim 17 , wherein the housing comprises a ledge around a periphery of the opening. 
     
     
         21 . The circuit of  claim 17 , wherein the cavity between the lid wafer the base wafer comprise a port to allow fluid communication with the cavity defined by the housing. 
     
     
         22 . The circuit of  claim 17 , wherein the lid wafer, the base wafer, and the housing are comprised of any combination of glass, silicon, or ceramic. 
     
     
         23 . The circuit of  claim 17 , wherein the lid wafer comprises a second capacitive plate. 
     
     
         24 . A circuit comprising:
 a housing comprising a plurality of walls defining a first cavity and an opening;   a sensor connected to the housing at the opening, the sensor comprising:
 a lid wafer comprising an electrode; 
 a base wafer comprising an electrode, wherein the base wafer is positioned entirely within the first cavity and the base wafer is bonded to the lid wafer, the lid wafer and base wafer defining a second cavity; and 
 an electrical via electrically connecting the electrode of the base wafer to a contact on an other side of the base wafer.